Field of the Invention
The invention relates to a method for the production of a heat exchanger, particularly a sorption heat exchanger.
Description of the Background Art
Heat exchangers having ferrous based components are subject to specifications with respect to the tightness of the passages carrying the medium to the outside as well as the media against one another. If the leak rate exceeds a threshold value determined depending on the application, the heat exchanger must be discarded as a reject. Ferrous based heat exchangers which must meet demanding tightness criteria are often joined by welding, particularly laser welding, or by high temperature brazing. In doing so it is essential that the joining seam between the joints does not exceed certain widths, for example 0.2 mm, since otherwise the quality of the joint suffers or a gas proof joint might not materialize. However, the widths of such joints can often not be kept at the desired small seam width due to the production tolerance and the forming processes of the semi-manufactured products.
In order to overcome the discrepancy between the small necessary seam widths of the joint and the corresponding production tolerances of the semi-manufactured products, it is common to soft-solder the pre-coated components of the stainless steel heat exchanger. With low soldering temperatures this process can bridge the previously mentioned greater seam widths.
From WO 2010/112433 A2, which corresponds to US2012090345, which is incorporated herein by reference, a sorption heat exchanger is known which has flat tubes with a clear diameter of typically 1 mm through which a gas or a fluid flows and which may not be closed by the soldering process. In a typical immersion process the liquid brazing solder, driven by the capillary force, would flow into the flat tube and close it at least in part, thereby limiting the efficiency of the sorption heat exchanger.
A method for the manufacturing of a heat exchanger is known from DE 2 030 925 A1, which corresponds to U.S. Pat. No. 3,689,941, in which a ferrite stainless steel base material is first given a thin Sn—Pb coating, the components of a heat exchanger are produced from the coated semi-manufactured product through forming, and lastly the complicated heat exchanger is assembled by using flux material and is joined into a fluid tight heat exchanger with another Sn—Pb brazing solder.
DE 4 309 500 A1, which corresponds to U.S. Pat. No. 5,395,702, and which discloses a method for the immersion coating of a Fe-based semi-manufactured material, in particular a stainless steel semi-manufactured product, with a tinny alloy with at least 90% weight-% tin. This protects the emerging coated sheet. The tin coated stainless steel material is used as a top panel.
DE 2 435 925 A1, which corresponds to U.S. Pat. No. 3,963,162, and which describes a method for the soldering of stainless steel pipes, in which the stainless steel pipes are used as hot water pipes. A pipe joint with a defined clear diameter is filled with a soldering paste on tin basis, and after the fusing of the tin of the tin soldering paste an additional soft solder is added into the gap of the pipe joint.